System and methodology for establishing a fatigue life of a subsea landing string

ABSTRACT

A technique facilitates monitoring of a location susceptible to fatigue due to loading experienced along a subsea landing string or other subsea tubing string. Initially a location or locations susceptible to fatigue may be determined along the subsea tubing string. At least one sensor, e.g. a strain sensor, is placed along the tubing string proximate the location susceptible to fatigue. The strain sensor or sensors can then be used to collect data regarding loading incurred at the location. The loading data can then be used to determine fatigue at the location and/or at a device proximate the location.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 62/258,875, filed Nov. 23, 2015, of which is herein incorporated by reference in its entirety.

BACKGROUND

In subsea hydrocarbon well applications, various equipment is provided at the seabed. The subsea equipment may comprise a blowout preventer (BOP) and other equipment positioned proximate the seabed and above a wellbore extending into a subsea geologic formation. Surface equipment, e.g. a rig, may be located at a surface of the sea generally above the wellbore and various tubing strings may extend between the surface equipment and the subsea equipment. Depending on the application, the tubing string may comprise a riser and/or subsea landing string deployed from the surface equipment and down into cooperation with the BOP. In many of these applications, the tubing string is subjected to periodic loading due to wave action or other loads which occur during subsea operations. For example, a riser may be affected by stresses resulting from movement of the rig and from vortex induced vibrations which occur as ocean current flows past the tubing string and undergoes vortex shedding. Subsea landing strings may be protected from the vortex induced vibrations because of their relatively shorter length and protection by the BOP, but the subsea landing strings also experience load stresses due to movement of the rig and/or other operational effects. The fatigue resulting from the loading can shorten the lifetime of devices along the tubing string and of the overall tubing string.

SUMMARY

In general, a system and methodology are provided for monitoring a location susceptible to fatigue due to loading experienced along a subsea landing string or other subsea tubing string. Initially a location or locations susceptible to fatigue may be determined along the subsea tubing string. At least one sensor, e.g. a strain sensor, is placed along the tubing string proximate the location susceptible to fatigue. The strain sensor or sensors can then be used to collect data regarding loading incurred at the location. The loading data may then be used to determine fatigue at the location and/or at a device proximate the location.

However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

FIG. 1 is a schematic illustration of an example of a subsea well system comprising subsea equipment coupled with surface equipment by a tubing string, according to an embodiment of the disclosure;

FIG. 2 is a schematic illustration of an example of a subsea landing string disposed in a blowout preventer combined with sensors for monitoring loading effects, according to an embodiment of the disclosure;

FIG. 3 is a schematic illustration similar to that of FIG. 2 but showing examples of loads experienced at locations along the subsea landing string, according to an embodiment of the disclosure;

FIG. 4 is a cross-sectional view of a section of tubing string having a plurality of strain gauges mounted to the tubing string, according to an embodiment of the disclosure;

FIG. 5 is a schematic illustration of another example of a subsea landing string disposed in a blowout preventer combined with sensors for monitoring loading effects, according to an embodiment of the disclosure;

FIG. 6 is a schematic illustration of a location being monitored for loading effects, according to an embodiment of the disclosure;

FIG. 7 is a schematic illustration of another example of a subsea landing string combined with subsea a data recorder, according to an embodiment of the disclosure;

FIG. 8 is a schematic illustration of an example of a sensor mounted on a tubing string and combined with a telemetry system, according to an embodiment of the disclosure;

FIG. 9 is a schematic illustration of an example of a well system with sensors mounted on a tubing string combined with a wireless telemetry system for relaying loading data to a surface processing system for fatigue analysis, according to an embodiment of the disclosure; and

FIG. 10 is a schematic illustration of an example of a display used to display results of the fatigue analysis and estimates of remaining life of a subsea landing string device or other component, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

The present disclosure generally relates to a system and methodology for monitoring a location or locations susceptible to fatigue due to loading experienced along a subsea landing string or other subsea tubing string. Initially the location(s) susceptible to fatigue may be determined along the subsea tubing string. At least one sensor, e.g. strain sensor, is placed along the tubing string proximate the location susceptible to fatigue. The strain sensor or sensors can then be used to collect data regarding loading incurred at the location. The collected data may be processed and evaluated to determine fatigue at the location and/or at a device proximate the location. In some applications, for example, strain data obtained along a tubular member may be used to determine detrimental effects on an adjacent tubing string device. As described in greater detail below, the strain data may be used to predict a fatigue lifetime of a component, e.g. a device, disposed along the subsea landing string or other tubing string.

The system and methodology described herein may be used for fatigue monitoring in a subsea landing string deployed into a blowout preventer positioned at a seafloor. However, the assessment methodology also may be used for fatigue monitoring with respect to locations along a riser and/or other subsea tubing strings. The improved fatigue life monitoring enables the overall lifetime of components, e.g. tools, to be maximized by lowering the risk of failure due to fatigue damage. The system and methodology address many of the technical challenges associated with strain monitoring in a subsea environment, including challenges associated with pressure and temperature considerations and data transmission from a seabed to a rig floor. A surface processing system, e.g. computer-based processing system, or other processing system may be used to facilitate fatigue related data retrieval and archiving of the data for individual assets and jobs.

In some applications, real-time fatigue monitoring is enabled by transmitting sensor data, e.g. strain sensor data, from a subsea location to a surface processing system. A sensor or sensors may be disposed along the subsea tubing string for monitoring stresses experienced by the subsea tubing string due to, for example, movement of the surface rig, wave motion in the ocean, and/or other operationally induced stresses. For example, the system and methodology may be used to continuously monitor for extreme stresses caused by unusual rig movement or other types of load influences on the tubing string. Based on the data collected, the remaining life of a given tool may be calculated and subsequently updated to ensure an effective and efficient maintenance schedule with respect to the given tool.

In a specific example, strain sensors or other suitable sensors are deployed along a tool in the form of a subsea tubing string, e.g. a subsea landing string. The sensors disposed along the subsea landing string may be used for monitoring tool health at discrete, periodic locations along the length of the subsea landing string. The data collected may be used to ensure an adequate maintenance system with respect to the subsea landing string and its various components. The sensors and cooperating monitoring equipment enable measurement, recording, and transmission of strain data which is used to calculate fatigue related effects at various locations, e.g. at various devices, of the subsea landing string. The data obtained regarding fatigue related effects at specific locations can be used to establish fatigue life predictions. The sensor data also may be used with an appropriate computer modeling system to interpolate strain and fatigue calculations from measured points to less accessible points.

Referring generally to FIG. 1, an embodiment of a well system 20 is illustrated. In this embodiment, well system 20 is illustrated in an offshore environment in which surface equipment 22, e.g. a rig, is positioned at a sea surface 24 generally over a wellbore 26. The wellbore 26 is drilled into a subterranean formation 28 through a seafloor 30. In this example, the subsurface equipment 32 is located over wellbore 26 at seafloor 30. By way of example, the subsurface equipment 32 may comprise a blowout preventer 34.

A subsea tubing string 36 extends into cooperation with the blowout preventer 34. By way of example, the subsea tubing string 36 may comprise a subsea landing string 38 which extends into an interior of the blowout preventer 34. Additionally, a riser 40 may be deployed to extend from the rig 22 down toward blowout preventer 34. The riser 40 also is in the form of a subsea tubing string and may comprise various features, such as a quick connect 42. As described in greater detail below, a sensor system may be used to obtain data at specific locations so as to monitor fatigue at specific subsea tubing string locations resulting from loading caused by waves, currents, or other environmental or operational factors. Sensors may be deployed along landing string 38 and/or at other devices, e.g. at quick connect 42, to monitor for fatigue effects.

Fatigue related data may be processed on a suitable processing system 44, such as a surface, computer-based processing system. However, data processing may be performed in whole or in part at a subsea location, a surface location, and/or a remote location. Depending on the type of sensor system utilized for monitoring fatigue, the processing system 44 may comprise appropriate software modules 46 programmed to process data from the sensor system and to provide, for example, fatigue life predictions for specific subsea tubing string components. By way of example, the processing system 44 may be programmed with a suitable modeling program 48 which uses sensor data related to stresses incurred and historical stress data to determine estimates of fatigue life with respect to specific components, e.g. devices, disposed along one or more subsea tubing strings.

Referring generally to FIG. 2, an example of subsea tubing string 36 is illustrated in the form of subsea landing string 38 disposed within an interior 50 of blowout preventer 34. In this example, the subsea landing string 38 comprises various devices, such as a retainer valve 52 and a subsea test tree 54 coupled by tubular members 56, e.g. mandrels. A sensor system 58 comprises a sensor 60, and often a plurality of sensors 60, disposed along the subsea landing string 38. The sensors 60 are mounted at specific locations which facilitate collection of useful fatigue related data. In some applications, sensors 60 may be mounted directly to a device susceptible to fatigue, e.g. retainer valve 52 or subsea test tree 54. However, sensors 60 also may be mounted proximate the devices, e.g. along tubular members 56 coupled with the subject device, and data related to fatigue may be interpolated from the actual measurement locations to less accessible locations.

As further illustrated in FIG. 3, the sensors 60 may be positioned and arranged to monitor stresses incurred by the subsea landing string 38 or other subsea tubular string. By way of example, the sensors 60 may be positioned to monitor tensile loads as represented by arrow 62. The sensors 60 also may be used to monitor a variety of other types of loading experienced by the subsea landing string 38, such as torque loads, compressive loads, and/or oscillatory loads, e.g. wave loading, as represented by arrow 64. Depending on the application, the sensors 60 may comprise strain gauges, accelerometers, and/or other suitable sensors able to collect data related to the stress loading which can affect fatigue life of a given component/device.

Referring to FIG. 4, for example, an embodiment is illustrated in which sensors 60 are in the form of strain gauges 66. In this example, a plurality of the strain gauges 66 is secured to a housing 68 of the subsea landing string 38. By way of example, each strain gauge 66 may be coupled with a data storage and transmitter device 70 which also is secured to the subsea landing string housing 68. According to some embodiments, each device 70 may be mounted to the housing 68 via a ceramic insulator 72.

In some applications, a single strain gauge 66 may be affixed to the landing string housing 68, e.g. to an exterior surface of one of the tubular members 56 or one of the devices 52, 54. However, a plurality of strain gauges 66 or other types of sensors 60 may be used for a variety of reasons. For example, multiple strain gauges, e.g. multiple couples of strain gauges, may be used for redundancy. Additionally, monitoring of certain types of strain, e.g. strain resulting from bending, may be improved by using two or more strain gauges. As described in greater detail below, the data acquired by sensors 60/strain gauges 66 may be transmitted to a downhole storage device or to surface storage. In some applications, for example, the data obtained by sensors 60 may be transferred to the surface via a suitable wireless telemetry system.

As illustrated in FIG. 5, the subsea landing string 38 may be constructed in various configurations with different types of devices and components depending on the parameters of a given application. For example, the retainer valve 52 and subsea test tree 54 may comprise or work in cooperation with other features and devices. In the example illustrated in FIG. 5, the subsea test tree 54 comprises other components, such as a latch 74, a flapper valve 76, and a ball valve 78. The sensors 60 may be placed on these components to measure strain data directly or on members coupled with the these components for interpolation of strain data at specific, less accessible locations along the subsea landing string 38.

By way of example, a location 80 susceptible to fatigue may be at a threaded section 82, as illustrated in FIG. 6. In this example, the threaded region 82 is formed by a thin region or regions at the ends of tubular sections being joined. In some applications, the tubular members 56 may be joined to each other or to adjacent devices, e.g. devices 52, 54, by threaded region 82 thus establishing location 80 susceptible to fatigue. Sometimes placement of the sensor or sensors 60 directly at location 80 is difficult. However, the sensors 60 may be located proximate the location 80, as illustrated, and a transfer function may be used between the stresses/loads measured at the locations of sensors 60 and the loads at the location 80 susceptible to fatigue. By way of example, a finite element analysis may be performed by processing system 44 (or by another suitable processing system) to create the transfer function between measured loads at the sensor location and the loads acting on the devices at fatigue location 80. It should be noted the locations 80 susceptible to fatigue may occur at many types of connections and/or at many other positions along the subsea tubing string 36.

Referring generally to FIG. 7, an embodiment is illustrated in which a data recorder 84 is communicatively coupled with the sensor or sensors 60. By way of example, data recorder 84 may be in the form of a strain gauge recorder for collecting strain gauge data from one or more of the sensors 60. As illustrated, the data recorder 84 may be mounted at a subsea position along, for example, the subsea landing string 38. In some applications, the strain data and/or other data from data recorder 84 is retrieved when the subsea landing string 38 is retrieved to the surface. However, the data recorder also may be coupled with a telemetry system 86, as illustrated in Figure 8. The telemetry system 86 may be a wired telemetry system or a wireless, e.g. acoustic, telemetry system able to relay data from sensors 60 to the surface in real-time.

In a specific example, sensors 60 comprise strain gauges 66 which are connected to data recorder 84, and the data recorder is in the form of a strain gauge analog input box. The strain gauge analog input box may be connected to a telemetry system 86, such as the Muzik™ system available from Schlumberger Corporation. The Muzik™ system enables recording of sensor data in recorder mode or in recorder plus transmit/receive mode. If data is collected in record mode, the data may be exported once the data recorder 84 is retrieved to the surface. In the recorder plus transmit/receive mode at least some of the sensor data may be transmitted to the surface in real time.

Whether in real-time or at a later point in time, the sensor data, e.g. strain data, is provided to processing system 44. As illustrated in FIG. 9, some applications utilize real-time transfer of data to the surface and to processing system 44 via telemetry system 86 which may comprise wireless telemetry devices 88, e.g. acoustic devices, to facilitate the real-time, wireless transfer of sensor data. The real-time transfer of data enables continual monitoring of specific subsea locations 80 along the subsea tubing string 36, e.g. along subsea landing string 38, that are susceptible to fatigue.

The data collected by sensors 60 may be stored in a logbook 90 of processing system 44. For example, data may be collected from accelerometer sensors 60 and/or strain gauge sensors 60 and continuously used to update the logbook 90. Examples of data collected and stored in logbook 90 may include the number of stress events, maximum values of bending moments, mean values of bending moments, tensile loading, compressive loading, and/or other stress-related data at a specific location or locations 80 that can affect the fatigue life of a given component, e.g. device.

The processing system 44 also may store the ongoing data collected and may establish a database which tracks the collected data related to, for example, fatigue accumulation, maximum fatigue life expectation, and remaining lifecycle, for each selected component and each selected job. As described above, transfer functions, e.g. finite element analysis transfer functions, may be used to establish an equivalent fatigue evaluation at a location separate from the actual sensor locations. The logbook 90 may be updated continuously or after each job.

The data collected in logbook 90 may be continually processed via, for example, modeling program 48 to determine and update fatigue life estimates at specific locations 80, e.g. at specific devices, along the subsea landing string 38 or other tubing string. For example, the processing system 44 may utilize suitable software modules 46 and modeling programs 48 to perform the desired transfer functions and to perform the conversion of sensor data into estimates of fatigue life. In some applications, sensors 60 may comprise both strain gauges 66 to provide strain data and accelerometers to provide additional data, e.g. orientation, pipe angle, strain. The data from the different types of sensors 60 is then processed according to the desired models or algorithms to provide estimates of fatigue life at the location/devices susceptible to fatigue.

In some applications, the processing system 44 and modeling program 48 may utilize historical test data in which various types of tubing string components/devices have been tested to failure based on different types of strains. By matching measured strain data with historical test data for a comparable component/device, the processing system 44 is able to output and display estimates of fatigue life. As illustrated in FIG. 10, for example, graphical estimates 92 of remaining component life may be output on a display 94 of processing system 44. The estimates of fatigue life may then be used automatically or by intervention of an operator to adjust parameters of the operation, replace specific components, and/or take other actions to maximize the useful life of the subsea tubing string.

In an operational example, the locations 80 susceptible to fatigue due to stress loading are initially determined. The locations 80 may be on specific devices, at connections, e.g. threaded connections or moving pipe-in-pipe connections, or at other locations susceptible to fatigue during the subsea operation. In various subsea operations, for example, locations 80 are selected along subsea landing string 38 and/or at quick connect 42. Sensors 60 may be positioned at the location(s) 80 or at a suitable, related location which enables interpolation of stress loading experienced at the location(s) 80. The sensors 60 are then used to obtain loading data resulting from stresses to the tubing string.

The collected data may be stored in logbook 90 and processed via processing system 44 to make the desired mathematical conversions and to perform the desired modeling, e.g. comparison with historical data, to determine the effects of loading as it pertains to fatigue at the location(s) 80. The estimated effects on fatigue life of the component/location of interest may be output to, for example, display 94 for evaluation by an operator. Depending on the application, the output of results may be ongoing in real-time or may be at desired intervals.

Depending on the application, the well system 20 may have a variety of configurations and/or components. Similarly, the fatigue monitoring methodology may be used with many types of tubing strings in a variety of subsea applications. Depending on the application, a single sensor or a plurality of sensors may be used to obtain data at an individual location or multiple locations. Additionally, the sensor or sensors may comprise strain gauges and/or other types of sensors, e.g. accelerometers, to facilitate the accumulation of desired data. The data also may be processed according to a variety of computer models and/or according to various algorithms to determine the estimates of fatigue life for a given type of component.

Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. 

What is claimed is:
 1. A system for use in a well application, comprising: a blowout preventer disposed along a seafloor; a subsea landing string extending into the blowout preventer, the subsea landing string comprising a plurality of landing string devices coupled by tubular members; a plurality of sensors mounted on at least one of the tubular members, the sensors being operated to monitor stress loading at one or more specific locations along the subsea landing string; and a data recorder positioned to receive data from the plurality of sensors, the data providing an indicator of component fatigue at one or more locations.
 2. The system as recited in claim 1, wherein the plurality of sensors comprises a strain gauge.
 3. The system as recited in claim 1, wherein the plurality of sensors comprises an accelerometer.
 4. The system as recited in claim 1, wherein the plurality of sensors comprises a strain gauge and an accelerometer.
 5. The system as recited in claim 1, wherein the plurality of landing string devices comprises a retainer valve, the plurality of sensors being coupled to at least one tubular member connected to the retainer valve.
 6. The system as recited in claim 1, wherein the plurality of landing string devices comprises a subsea test tree, the plurality of sensors being coupled to at least one tubular member connected to the subsea test tree.
 7. The system as recited in claim 1, further comprising a sensor mounted on a quick connect.
 8. The system as recited in claim 1, further comprising a telemetry system for transmitting sensor data from the plurality of sensors to a surface location.
 9. The system as recited in claim 8, further comprising a surface processing system for receiving the sensor data, processing the sensor data, and outputting an estimate of fatigue life with respect to at least one of the landing string devices.
 10. A method, comprising: determining a location susceptible to fatigue along a subsea landing string; locating at least one sensor proximate the location susceptible to fatigue; deploying the subsea landing string into cooperation with a subsea blowout preventer; recording data from the at least one sensor; and determining a fatigue life estimate of a component of the subsea landing string based on the data.
 11. The method as recited in claim 10, wherein determining comprises determining location susceptible to fatigue based on tensile loading and wave loading.
 12. The method as recited in claim 10, wherein locating the at least one sensor comprises locating a plurality of sensors on tubular sections of the subsea landing string.
 13. The method as recited in claim 10, wherein locating the at least one sensor comprises locating the sensor along a tubular section of the subsea landing string connected with a landing string device.
 14. The method as recited in claim 10, wherein locating the at least one sensor comprises locating the sensor along a tubular section of the subsea landing string connected with a retaining valve.
 15. The method as recited in claim 10, wherein locating the at least one sensor comprises affixing the at least one sensor directly to a subsea landing string device.
 16. The method as recited in claim 10, further comprising transmitting the data to the surface in real time.
 17. The method as recited in claim 10, wherein locating comprises locating a strain sensor along a tubular element of the subsea landing string.
 18. A method, comprising: determining a location susceptible to fatigue along a subsea tubing string; placing a plurality of strain sensors proximate the location; using the plurality of strain sensors to collect data regarding loading at the location; and monitoring fatigue of a tubing string device by maintaining a log of the data collected.
 19. The method as recited in claim 18, wherein placing comprises placing the plurality of sensors along tubular elements coupled to a landing string component of the subsea tubing string; and wherein monitoring comprises processing the data collected to determine an estimated fatigue life of the landing string component.
 20. The method as recited in claim 18, further comprising using a telemetry system to transmit the data to the surface. 